IntroductionNon-small cell lung carcinomas (NSCLC) are characterized by their intrinsic résistance to chemotherapy. The Multidrug Résistance Protein (MRP) family belong to the ATP bin-ding cassette super family of transport proteins, which play a physiological rôle in defence against toxic compounds including carcinogens. Some MRPs hâve been shown to confer résistance to anticancer agents in variousin vitromodels.MethodsIn order to investigate the possible rôle of MRP1, -3 and -5 in clinical drug résistance, protein expression is analysed using immunohistochemistry on tumoral tissue section from patient who underwent surgery. Survival is analysed according to MRP expression using Kaplan-Meier analysis and a Log Rank test.MRPgène expression using RT-PCR is already in progress.Results61 tumoral frozen samples are used, 25 adenocarcino-mas (ADK) and 36 squamous cell carcinomas (SCC), collected from July 1998 to April 2004. 28 samples corne from patients who underwent adjuvant chemotherapy for an upgraded postoperative tumor. 35 tumorals samples do not express MRP1, -3 or -5. For the positive sample investigated, MRP3 is positive for ail ADK, MRP1 and -5 are inconstantly expressed. For the positive SCC, ail samples except one, are positive for MRP1, and only one sample hâve positive expression for MRP5 and for MRP3. Survival analysed using Kaplan-Meier analysis and a Log Rank test for the 28 patients who underwent adjuvant chemotherapy show that overall médian survival is 20 months. Médian survival for the patient who hâve none positive MRP expression is 65 months and for patients who hâve at less one positive MRP protein expression, the médian survival is 16 months. This différence is not statistically significant (small sample size).ConclusionsOnly 42,6% of samples hâve a positive expression for at less one of the MRP, ADK express constantly MRP3 and SCC express MRPlmajoritary. The médian survival for patient who underwent adjuvant chemotherapy decrease from 65 to 16 months, when at less one MRP is expressed. This suggest that MRP could be involved in chemotherapy response. More samples are investigated to confort thèse results andMRPsgène expression are also investigated and quantified using RT-PCR for thèse patients.